The Jinshajiang suture zone: tectono-stratigraphic subdivision and revision of age  

作　　者：汪啸风 lan Metcalfe 简平 何龙清 王传尚 

机构地区：[1]LYichang Institute of Geology and Mineral Resources, Chinese Academy of Geological Sciences, Yichang 443003,China [2]Asia Centre, University of New England, Australia

出　　处：《Science China Earth Sciences》2000年第1期10-22,共13页中国科学（地球科学英文版）

摘　　要：Integrated study of rock assemblage, tectonic setting, geochemical feature, fossil contained and isotopic geochronology on the metamorphic mixed bodies, exposed in the Jinshajiang suture zone, suggests that one informal lithostratigraphic unit, the Eaqing Complex, and three tectono-stratigraphic units, the Jinshajiang ophiolitic melange, the Gajinxueshan Group and the Zhongxinrong Group, can be recognized there. It is first pointed out that the redefined Eaqing Complex might represent the Meso- to Neo-Proterozoic remnant metamorphic basement or mi-crocontinental fragment in the Jinshajiang area. The original rocks of it should be older than (1627 ±192) Ma based on the geochronological study. The zircon U-Pb age of plagiogranites within the Jinshajiang ophiolitic assemblage is dated for the first time at (294 ± 3) Ma and (340 ± 3) Ma respectively. The Jinshajiang ophiolite is approximately equivalent to the Ailaoshan ophiolite in the formation age, covering the interval from the Late Devonian to the Carboniferous. Dating of U-Pb age from basalt interbeds indicates that the redefined Gajinxueshan Group and Zhongxinrong Group may be considered Carboniferous to Permian and latest Permian to Middle Triassic in age. In geotectonic terms the Jinshajiang suture zone is thought to be a back-arc basin in the eastern margin of the Paleo-Tethys. This back-arc basin started in the Late Devonian, and formed in the Devonian-Carboniferous. The collision event around the Permian/Triassic boundary to the Middle Triassic led to the closure of the back-arc basin and formation of suture.Integrated study of rock assemblage, tectonic setting, geochemical feature, fossil contained and isotopic geochronology on the metamorphic mixed bodies, exposed in the Jinshajiang suture zone, suggests that one informal lithostratigraphic unit, the Eaqing Complex, and three tec-tono-stratigraphic units, the Jinshajiang ophiolitic melange, the Gajinxueshan Group and the Zhongxinrong Group, can be recognized there. It is first pointed out that the redefined Eaqing Complex might represent the Meso- to Neo-Proterozoic remnant metamorphic basement or mi-crocontinental fragment in the Jinshajiang area. The original rocks of it should be older than (1627 ±192) Ma based on the geochronological study. The zircon U-Pb age of plagiogranites within the Jinshajiang ophiolitic assemblage is dated for the first time at (294±3) Ma and (340±3) Ma respectively. The Jinshajiang ophiolite is approximately equivalent to the Ailaoshan ophiolite in the formation age, covering the interval from the Late Devonian to the

关 键 词：Jinshajiang SUTURE zone complex ophiolitic MELANGE Paleo-Tethys. 

分 类 号：P539[天文地球—古生物学与地层学]